This invention relates to the field of data communications and especially to methods and systems for delivering content files efficiently. The invention relates in particular to methods and systems for requesting, storing, and delivering large and very large content files from a remote content provider to a content file client device such as a laptop computer using a browser, a personal data assistant, or a cell phone.
Multimedia digital information files such as audio, video, movies, and the like are relatively large as compared to most other types of files which are downloaded via the Internet. Frequently a request is made from a client computer to a content provider web site and the large file is not immediately available due to network congestion, too much current traffic, prioritizations, and capacity limitations.
Among the previously proposed and used methods and systems for delivering content in general to client computers are content delivery networks which include content brokers and edge servers, which are a form of cache servers located in strategic geographic locations. Content delivery networks can cache content in cache servers, known in such networks as edge servers because they are located at strategic geographic locations near the edge of the network, from which content can be available to client computers even in cases of network congestion and outage.
Various techniques are described in an Akamai Networks, Inc. White Paper entitled Internet Bottlenecks: the Case for Edge Delivery Services, and a Network Working Group Internet Draft of Apr. 3, 2003 entitled Known CN Request-Routing Mechanisms, Barbir, et al.
Content delivery networks are also described in U.S. Patent Publications 20030065762 of Apr. 3, 2003; 20030002484 of Jan. 2, 2003; and Leighton et al, U.S. Pat. No. 6,108,703. The method of tagging content for delivery from the content delivery network using a migratory and a rewrite tool which rewrites URLs to point to the edge server most likely to host the requested content is disclosed in these publications and patent.
Other content delivery type networks for television broadcasting, live performances, music juke boxes, global networks and data delivery systems are described in the following references: International Publication No. WO 03/034704 published Apr. 24, 2003; U.S. Patent Publication No. 2002/0026512; “The Interactive Multimedia Jukebox (IMJ): a new paradigm for the on-demand delivery of audio/video”, Kevin C. Almeroth, Mostafa H. Ammar, Computer Networks and ISDN Systems 30 (1998) 431-441, 1998; U.S. Pat. No. 6,108,703; and International Publication No. WO 02/08856 published Jan. 31, 2002.
Prior content delivery networks distribute content based on past, i.e., historical, information. Obtaining content availability information from content delivery-networks, a content provider can redirect a content uniform resource locator (URL) to an edge server that is closer to the requesting client in order to speed up) the downloading of the content file to the client. The content provider may fail to redirect a content URL to an edge server closer to requesting client because the content is not currently available on any of those edge servers. In some cases a user will be willing to tolerate delays in delivery of large content files such as multimedia files for a variety of reasons, for example the user may not need to use the file immediately or may be requesting the file from a personal data assistant or web-enabled cellular phone and may wish to have the file streamed at a future time because of time constraint or may not be able to use the file because of capacity constraint of the requesting device.
In a downloading service model, for example, a content request does not necessarily reflect that there is an immediate need for the content. Therefore, even if a piece of content is currently not available on an edge server, if the content delivery network can deliver the content to the edge server at a future time, the content provider can satisfy the need of a user by redirecting the request to the edge server.
While present content delivery networks improve the delivery of content files to client computers, as content files become larger and use of the Internet to request and obtain multimedia files becomes more prevalent, further improvements to content delivery systems and methods are needed to provide a satisfactory delivery rates.